Is putting on a poker face the most effective strategy in cards? People talk about spotting players’ ‘tells’, involuntary behavior that gave away their confidence level. To prevent people from picking up on your tells, you were supposed to work on a poker face – a blank look that gives nothing away.

But instead of shutting down and sending no signals, can we send misleading signals?

Participants made risky choices in a simplified poker task while being presented opponents whose faces differentially correlated with subjective impressions of trust… [P]eople took significantly longer and made more mistakes against emotionally positive opponents… According to these results, the best “poker face” for bluffing may not be a neutral face, but rather a face that contains emotional correlates of trustworthiness. Moreover, it suggests that rapid impressions of an opponent play an important role in competitive games, especially when people have little or no experience with an opponent.

[Quick note: As I read through the procedure, I wasn’t sure that I agreed with their assessment of ‘mistake’ in this simplified version of poker. I’ll look into it, but it’s still interesting to note that people folded more against trustworthy-looking faces]

It’s a natural habit to develop – a if a person looks confident and trustworthy, we’re more likely to believe them if they say they have an advantage (by, say, betting). They provide an image which I think lays it out well:

We have access to the information in grey – our own cards, our opponent’s bet, and our opponent’s facial expression. We’re trying to make a decision based on how our cards compare to theirs – which is unknown. Their style is also unknown, which is a problem because it’s a hidden factor influencing their bet.

Since we can only work with the information we have, we go backward: given the face we see, what is their style/attitude? Given their style and bet, what cards do they have? Of course, the random static computerized faces weren’t ‘inadvertently’ giving cues, but we’ve unconsciously learned to treat facial cues are a vital part of figuring out how the bet correlates to cards.

So is a trustworthy smile better than a blank poker face? As the authors point out, the study holds for first impressions, “when people have little or no experience with an opponent.” I would love to see a study of how long the effect holds up. After repeated interaction with the trustworthy-looking computer opponent, do people adapt and re-calibrate the assumed face-to-attitude correlation? I expect there to be some difference even over time – the unconscious connection is tough to shake. But its impact would diminish.

Perhaps we can smile and look trustworthy whenever we want opponents to fold? Sending misleading information is a powerful tool in game-theory. But I suspect decent card players would adapt quickly. Unless you’re damn confident that you know how to exploit their assumptions, you’ll be giving them an edge. Poker faces give up the chance to send intentional false information, but it also cuts out the unintentional cues we’re not even aware of.

Professor Quirrell had remarked over their lunch that Harry really needed to conceal his state of mind better than putting on a blank face when someone discussed a dangerous topic, and had explained about one-level deceptions, two-level deceptions, and so on. So either Severus was in fact modeling Harry as a one-level player, which made Severus himself two-level, and Harry’s three-level move had been successful; or Severus was a four-level player and wanted Harry to think the deception had been successful. Harry, smiling, had asked Professor Quirrell what level he played at, and Professor Quirrell, also smiling, had responded, One level higher than you.

Against true amateurs in a little house game, I’ll try some one-level deceptions. But when I’m in a new place with good players, I tend to play it safe and focus my energy on staying blank rather than on sending false signals.